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NOAA - 01/26/2023


When solar activity is high, Earth's upper atmosphere puffs up like a marshmallow held over a campfire. That's happening now. Since Solar Cycle 25 began, the Thermosphere Climate Index (TCI) has increased nearly 10-fold:






TCI is a number published daily by NASA, which tells us how hot Earth’s upper atmosphere is. The thermosphere, the very highest layer of our atmosphere, literally touches space and is a sort of "first responder" to solar activity.

Linda Hunt of Science Systems and Applications, Inc. created the plot, above, which shows how TCI during Solar Cycle 25 compares to other solar cycles of the past. So far, the thermosphere is about twice as warm during Solar Cycle 25 as it was at the same point in the previous solar cycle: data.

"The sun is coming more alive now and looks ready to make a run at exceeding the max TCI of Solar Cycle 24," notes Dr. Marty Mlynczak of NASA.

As the thermosphere puffs up, it increases aerodynamic drag on Earth-orbiting satellites. Indeed, this is a key reason for the loss of dozens of Starlink satellites in Feb. 2022. If current trends continue, drag will increase even more as Solar Cycle 25 reaches its peak (Solar Maximum) in 2024 or 2025.

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